1. Field of the Invention
Our invention relates to a system for sensing or locating the peaks of an output produced by a magnetic head as same reads digital or other information stored on a magnetic recording medium such as tape. More specifically, our invention is directed to improvements in such a system intended to enhance the accuracy with which the peaks of a magnetic head output are sensed or located.
2. Description of the Prior Art
A peak sensing system has been suggested which comprises an amplifier connected to a magnetic head, a half-wave rectifier, a slicer circuit, a differentiating circuit, a comparator circuit, and a pulse trailing edge sensing circuit (shown in FIG. 1 of the accompanying drawings). The slicer circuit (known also as an amplitude gate) interposed between half-wave rectifier and differentiating circuit of this prior art system is intended to block the passage therethrough of noise which may be contained in the output from the magnetic head.
Since, however, the slicer circuit permits the passage therethrough of only those portions of the amplified and half-wave rectified output from the magnetic head which lie above a relatively high boundary amplitude level, the amplitude of the output from the subsequently connected differentiating circuit becomes so small that the differential between the upper and the lower levels or "trip points" of the reference voltage of the comparator circuit must be minimized.
Thus, in event the output from the differentiating circuit has some high frequency noise superposed thereon, the comparator circuit is highly likely to respond unnecessarily to such noise, producing a rapid succession of output pulses. These undesired comparator output pulses cause the subsequent pulse trailing edge sensing circuit to produce corresponding output pulses out of agreement with the peaks of the output from the magnetic head.